Cancer Research UK has shared exclusively with GB News the "stark" increase in traffic to its website following King Charles and the Princess of Wales's cancer messages.
The pair have been praised for their "bravery" in discussing the topic, with them being credited for "destigmatising" cancer.
Senior health information officer at Cancer Research UK, Amy Hirst, explained the royals' videos had a major impact.
Ms Hirst told the People's Channel: "In the 24 hours following His Majesty's announcement over Christmas, we saw a 33 per cent increase in our Cancer Information web pages."
Cancer Research UK shared data exclusively with GB News
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She continued: "Over the course of the following week, there were over 730,000 visits, which is a 12 per cent increase compared to the usual weekly average, which is about 650,000.
"Similarly to the day of the princess's diagnosis, there were over 200,000 visits to our campus web pages, so around a 15.2 per cent increase compared to the day before the announcement. So it's really stark.
"When someone in the public eye shares their experience with cancer, Cancer Research UK does see that impact.
"That includes more calls to the nurse helpline, all visits to our general information pages, just that general increase."
In the 24 hours following His Majesty's announcement over Christmas, Cancer Research UK saw a 33 per cent increase in its Cancer Information web pages
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Ms Hirst acknowledged the "courage" from the royals to "share their experience that affects so many of us".
She said: "Cancer can affect anyone. The bravery of the princess and the King, coming forward with their story, knowing that they've got a lot of eyes on them - it's so brave.
"We really appreciate that hope and honesty. It's that really important reminder for people to listen to their bodies when something doesn't look or feel quite right.
"And the more we talk about cancer, the better, and we have made a lot of progress in research. There is hope."
The Princess of Wales said she was in remission from cancer in 2025 | REUTERSPart of the King's message in December focused on getting tested early for the disease, with the likelihood that "treatments will be more successful" if detected sooner rather than later.
Ms Hirst explained: "In most cases, it won't be cancer, but if it is, spotting it early means it could make all the difference.
"The screening checker is still up, so we'll keep on monitoring it. That's screenchecker.com, so hopefully people still are able to find that.
"It just helps people understand if they might be eligible for cancer screening and gives people really helpful tips and advice from a team of celebrities to help tackle common barriers."
In December, the King emphasised the importance of early diagnosis
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His Majesty said it "troubles me deeply" that millions of people across the UK are missing opportunities for early cancer diagnosis.
He told the public: "I know from my own experience that a cancer diagnosis can feel overwhelming. Yet I also know that early detection is the key that can transform treatment journeys, giving invaluable time to medical teams - and, to their patients, the precious gift of hope."
He told viewers that those gifts were ones "we can all help deliver", before praising what he described as the "community of care" surrounding cancer patients.
The King said he had been "profoundly moved" by the specialists, nurses, researchers and volunteers who "work tirelessly to save and improve lives".